How to convert data type to string in MySQL

MySQL is an open source relational database management system that is widely used in various application scenarios. During the use of MySQL, it is often necessary to convert various data types into strings. This article will introduce how to convert data types in MySQL into strings.

1. String functions

MySQL provides a wealth of string functions that can be used for string processing and conversion. Below we will introduce several commonly used string functions.

1. CAST

The CAST function can convert various data types in MySQL into string types. The syntax is as follows:

CAST(expression AS CHAR)

where expression is the data type to be converted, and AS CHAR means converting it into a string type. For example:

SELECT CAST(3.14 AS CHAR);

The above statement will return the string "3.14".

2. CONCAT

The CONCAT function is used to concatenate multiple strings into one string. The syntax is as follows:

CONCAT(str1, str2, ...)

where str1, str2, etc. are the strings that need to be spliced. For example:

SELECT CONCAT('hello', ' ', 'world');

The above statement will return the string "hello world".

3. CONCAT_WS

The CONCAT_WS function is also used to splice strings, but the difference is that it can specify a separator. The syntax is as follows:

CONCAT_WS(separator, str1, str2, ...)

where separator is the separator, str1, str2, etc. are the strings that need to be spliced. For example:

SELECT CONCAT_WS(',', 'apple', 'banana', 'orange');

The above statement will return the string "apple, banana, orange".

2. Convert date and time types into strings

The date and time types in MySQL can also be converted into strings. Below we will introduce several commonly used date and time type conversion functions.

1. DATE_FORMAT

The DATE_FORMAT function can convert date type into a string in a specified format. The syntax is as follows:

DATE_FORMAT(date,format)

where date is date type data and format is date format string. For example:

SELECT DATE_FORMAT(NOW(),'%Y-%m-%d %H:%i:%s');

The above statement will return the string representation of the current time in the format of "year-month-day hour:minute:second".

2. TIME_FORMAT

TIME_FORMAT function is used to convert time type data into a string in a specified format. The syntax is as follows:

TIME_FORMAT(time, format)

where time is time type data and format is time format string. For example:

SELECT TIME_FORMAT('12:34:56', '%H:%i:%s');

The above statement will return the string representation of the time "12:34:56" in the format of "hour:minute:second".

3. Convert numeric types into strings

Numeric types in MySQL can also be converted into strings. Below we will introduce several commonly used digital type conversion functions.

1. ROUND

ROUND function is used to round numbers and convert them into the specified format. The syntax is as follows:

ROUND(number, decimal_places)

where number is the number to be converted, and decimal_places is the number of decimal places to be retained. For example:

SELECT ROUND(3.1415926, 2);

The above statement will return the string representation of the value "3.14".

2. FORMAT

The FORMAT function is used to convert a number into a string represented by thousands separators. The syntax is as follows:

FORMAT(number, decimal_places)

where number is the number to be converted, and decimal_places is the number of decimal places to be retained. For example:

SELECT FORMAT(1234567.89, 2);

The above statement will return the string "1,234,567.89".

Conclusion

To convert various data types in MySQL to string types, you can use the rich string functions in MySQL. Date and time types and numeric types in MySQL can also be easily converted into string types. Being familiar with the use of these functions can allow us to perform MySQL-related data processing and calculations more efficiently.

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